1. Technical Field
The present invention relates to a semiconductor device and a method for cutting electric fuse, and particularly relates to a semiconductor device including an electric fuse and a method for cutting such electric fuse.
2. Related Art
A technology is conventionally known, in which a fuse is mounted in a semiconductor device, and the electric fuse is broken, so that a value of a resistor employed in the semiconductor device is suitably adjusted, or a failure element is separated and replaced into a normal element.
Typical manner for cutting a fuse includes cutting an electric fuse by irradiating a laser beam in a portion of the fuse and cutting a fuse by applying an electric current.
U.S. Pat. No. 4,064,493, Japanese Laid-open patent publication No. 2005-39,220 and Japanese Laid-open patent publication No. 2005-57,186 disclose an electric fuse, which is capable of being broken by utilizing a phenomenon, in which a material constituting the electric fuse migrates by an electromigration.
Japanese Laid-open patent publication No. 2005-39,220 discloses an electric fuse, which is breakable with a smaller current. In Japanese Laid-open patent publication No. 2005-39,220, an electric conductor constituting an electric fuse is formed to have a geometry that the conductor is turned back for several folds. FIG. 9 is a plan view, showing an electric fuse disclosed in Japanese Laid-open patent publication No. 2005-39,220. In this case, a fuse 1100 includes two folds of turn-back.
The fuse 1100 includes a current inflow terminal 1101 and a current drain terminal 1102, and further includes a first forward path straight line 1103, a return path straight line 1104 and a second forward path straight line 1113 between both of the terminals. The fuse 1100 further includes a first perpendicular coupling portion 1106, which provides a coupling between the first forward path straight line 1103 and the return path straight line 1104, and a second perpendicular coupling portion 1107, which provides a coupling between the second forward path straight line 1113 and the return path straight line 1104. When a predetermined current is supplied from current inflow terminal 1101 into current drain terminal 1102 in the fuse 1100 having the above-described configuration, the heats generated in the hatched portions 1108 outside of the fuse 1100 are added to the heats generated in the hatched portions 1109 inside of the fuse 1100, accelerating the breaking of the return path straight line 1104 sandwiched with the hatched portions 1109. This provides easily cutting the fuse 1100.
Moreover, Japanese Laid-open patent publication No. 2005-57,186 has disclosed a configuration in which, when a current is applied to a fuse, heat generated in a portion of the fuse, which is to be cut, is trapped or accumulated in the neighborhood of the portion in the fuse, which is to be cut, by enclosing the portion with a plate.
Japanese Laid-open patent publication No. 2004-186,590 discloses a semiconductor device, which is provided with an electrically conducting layer and an insulating film formed in this order in or above a semiconductor substrate, and also provided with a connecting hole that extends through the insulating film and reaches an upper surface of the conducting layer. The semiconductor device includes an interconnect layer, which includes a flat portion formed on the insulating film and a curved portion formed integrally with the flat portion and formed on a side surface and a bottom surface of the connecting hole, the curved portion defining a hollow portion that has a geometry tapered toward an upside thereof In this case, a geometry of the interconnect layer formed in the connecting hole is curved, and have a reduced thickness in the lower portion of the connecting hole. The structure of such interconnect layer is a fuse element structure, and a resistivity thereof is increased as the thickness is reduced, so that a minimum current value for cutting an electrical coupling between the lower interconnect layer and the overlying interconnect layer can be reduced. It is described that such configuration provides a simultaneous pursuit of a suitable fuse element structure, which is capable of being broken with a smaller current density, and a suitable multiple-layered interconnect structure.
The present inventor has recognized as follows. The hollow portion is formed in the connecting hole in a condition before cutting the fuse element in the technology described in Japanese Laid-open patent publication No. 2004-186,590. Therefore, an extra operation is additionally required for forming such the hollow portion. Further, it is required to form an insulating film on the hollow portion under a process condition that avoids filling the hollow portion, leading to limiting the formation method of the insulating film. Further, such fuse element structure may also causes a problem, in which the structure can not be manufactured simultaneously with forming a dual damascene multiple-layered interconnect structure that involves simultaneously forming vias and interconnects.
Further, it is also considered as described in U.S. Pat. No. 4,064,493, Japanese Laid-open patent publication No. 2005-39,220 and Japanese Laid-open patent publication No. 2005-57,186 that, when a fuse is broken by employing a phenomenon that a material constituting the fuse migrates via an electromigration, a heat treatment conducted on the semiconductor device after the cutting of the fuse may possibly cause a migration of the material via an electromigration again to re-connecting the fuse at the broken point If such unwanted re-connection is created, an appropriate result of a detection of a cutting status of the electric fuse can not be obtained, even if the electric fuse to be cut is cut once.
Although it is considered that a possibility of occurring the re-connection as described above is not very high and thus there is no problem in employing thereof for ordinary operations, it is required to enhance a property for maintaining a cutting condition of the electric fuse, when a reliability of the semiconductor device is highly demanded or when the semiconductor device is employed in extreme conditions.
The present inventor has found a novel technique for cutting electric fuses by utilizing an electric current, which is different from conventional method for cutting fuses.